BK 400 CRT Tester

[SkyLlama]

I've needed a CRT Tester for a while now as I'd rather give the CRTs in my TVs a check before I restore them, just so I know what to expect.

I didn't want to go to eBay so I took a drive to the place where the local TV repair man lives. He's a nice older guy who's been in the business for years now, but hasn't done much CRT work in a long time.

I asked if he had a tester and at first he thought he'd gotten rid of it, but upon going into the back of his shop he pulled out this, a BK 400 and sent me home with it.



It a rough looking unit, I'll give it that. Imagine how many TVs this things has seen in it's days.

It has all the adapters and such in a spot along the bottom.

Here is another shot of the front of it.



It's not great looking, but I opened it up and all the internals look good, spare for two caps that might be a problem at some point.

First things first: How do I test the tester and make sure it's functioning properly? I did plug it in to try, but I got no response from it at all.

And then how do I go about testing a CRT? I've never done it before and don't want to potentially damage anything.

[earlyfilm]

Originally Posted by SkyLlama

And then how do I go about testing a CRT? I've never done it before and don't want to potentially damage anything.

First, replace both capacitors with 600 V new parts.

Second, check the resitors for correct value. These testers are often found with resistors that have been given a hot foot by a shorted tube.

Only if the switches seem to be poorly making contact, clean the switch with a traditional (non-Oxy type) cleaner.

Have someone with a tube tester test the one tube in this tester.

Read the manual.

Ask if the owner still has his, if not down load my CRT 400 which is in the 6th post in this thread:

http://videokarma.org/showthread.php?t=254627

Standardize your testing procedure. Turn on the tester and let the filament warm up 5 minutes. Then do the shorts test while gently thumping the CRT neck at two points 90 degrees apart. Then do the emission test.

Never, not never nohow, ever do a rejuvination test with this tester, unless the tube shows a short. Even then, try to find a tester with a better shorts burn circuit.

If the tube is just low in emission, let the filament burn 24 hours at its rated voltage and retest. This helps to wake up tubes that have not been used in many years. Same thing if the tube looks gassy.

James

[Electronic M]

Boosting filament voltage a volt or two higher for a couple of hours is also a safe way of boosting emissions.

[radiotvnut]

I agree about the rejuvenation. My first CRT tester, back around '91, was a blue B&K 465 from the late '60's that was given to me by a TV shop who no longer used it. Back then, most of the TV's that I was working on were either B&W or delta gun color and the 465 did a good job of checking those tubes; however, it's rejuvenate function was the same as yours. I used it very carefully to rejuvenate some of the older big neck B&W CRT's; but, I never went higher than the lowest setting. Even doing it that way, I still torched a number of CRT's. I don't think I ever successfully rejuvenated a color tube with it and I learned to never attempt rejuvenation of the newer small neck 9"/12" B&W CRT's. It wasn't long before I invested in a newer B&K 470 that would test virtually any tube and had a much safer rejuvenation feature.

[DavGoodlin]

The B&K 400 looks similar to the B&K 445 I got recently. It really tests well but, as the experts above say, the "dynamic intensifier" is a crude and risky thing.

When I re-cap mine, I will disconnect that button. The "life test" button is very useful.

[radiotvnut]

It should be called "dynamic stripifier".

[davet753]

I had one of those, and I can testify that they will sure jolt the hell out of a picture tube. I always used my newer B&K, but held on to the 400 for the worst ones.

I burnt several up with that old thing, but I also brought some back to life that were headed for the scrap heap.